Small cleanup to notes in discussion and summary
In section 2.3.1, highlight hierarchical models

text. It doesnt appear to add to the argument. We are not
particularly stating problems with these models. I imagine
problems in the implementation do exist, but we need to
state them (such as, and Im guessing, "HIERARCH model
results in scattering metadata throughout the file and is
not particularly easy to reconstruct without the help of
specialized software")
Red mark last para in Units section 2.2.5

This appears dangerously close to suggesting action by
the FITS community. That content probably should go
now somewhere in the discussion, section 3.
Red mark section on compression as needing further

work, potentially. We need to have a very strong and
clear argument here as many in the FITS community feel
that compression is one of the things FITS does 'right'.
Red mark text on grouping convention in 2.4.6.

Not sure what that adds to the paragraph, looks like a
stray thought.
Red mark content in 2.4.6 which looks like it is

meant to be in the discussion, section 3.
Fix color{ref} -> color{red}